This invention relates to semiconductor materials. More particularly, it is concerned with methods of producing conductive members on the surfaces of substrates of semiconductor material.
In the fabrication of compound semiconductor devices, for example GaAs, different metallization systems are employed for forming Schottky barrier contacts, ohmic contact to N-type material, and ohmic contacts to P-type material. Typically, refractory metal Schottky barrier contacts are formed by sputtering tungsten or tungsten silicide over the substrate surface and then patterning by employing well known photolithography liftoff and metal etching techniques. Ohmic contacts to GaAs are formed by photolithography and metal liftoff techniques using different metal systems depending whether the ohmic contact is to N-type or P-type material. That is, for each of these contacts a different metallization system and a separate set of processing steps is required. If more than one type of contact is required, there are problems in obtaining accurate alignment between processes.